INVERTEBRATE PALEONTOLOGY. 269 



Entails! paupercula, M. & H. 



Plate 18, fig. 14. 



Denialium pauper culum, Meek and Hayden (I860), Proceed. Acad. Nat. Sci. Philad., XII, 178.— Meek (18G4) 

 Smithsonian Check-List N. Am. Cret. Fossils, 17. 



Shell small, arcuate, tapering rather gradually; section circular; sub- 

 stance comparatively thick ; surface smooth, but showing under a magnifier 

 extremely fine obscure lines of growth, which pass around somewhat 

 obliquely. 



Length of an imperfect specimen, measuring from the apex, 0.36 inch ; 

 diameter of same at apex, 0.03 inch ; diameter at larger extremity, 0.06 inch. 



I have not yet seen an entire specimen of this species, and even frag- 

 ments of it are rare. Its most marked peculiarities are its small size and 

 smooth surface. In the latter character, it differs from all the Cretaceous 

 species known to me excepting D. arcotinum, Forbes (Trans. Geol. Soc. Lon- 

 don, vol. VII, pi. 12, fig. 16), from the Cretaceous rocks of Southern India 

 It differs, however, from that species in being more arcuate and less robust. 



I ouly place this species provisionally in this group, on account of its 

 being entirely smooth, not having seen any specimens in a condition to show 

 the characteristic posterior slit. If the smooth forms without any posterior 

 marginal slit, for which Dr. Stoliczka proposes to retain Aldrovandus'sold pre- 

 Linnseau name Antale, are distinct from Dentalium proper, and, as he thinks 

 generically identical with Entalium, Defiance, then it is quite probable that 

 this species may be found to belong to that group, and have to take the name 

 Entalium pauperculum. 



Locality and position. — Moreau River; from the Fox Hills group of the 

 Upper Missouri Cretaceous series. Fragments, apparently of the same, have 

 also been seen in masses of rock from the Fort Pierre group of the same 

 scries. 



